Examples of solar spectral shells in $(f_0,\frac{\mathrm{d}{f}_0}{\mathrm{d}v})$ shell space. Left: an original spectrum from HARPS-N observation is transformed into the $(f_0,\frac{\mathrm{d}{f}_0}{\mathrm{d}v})$ shell space. Middle: solar spectral shell due to a Doppler effect. The Doppler shell is obtained by injecting a 5 m s⁻¹ Doppler shift into the HARPS-N solar master spectrum f₀. Right: solar spectral shell due to spectral shape change. We derived the shape shell by projecting the original shell onto the Doppler shell and subtracting the component due to Doppler effect from the original shell.